Abstract
Flow-directed pulmonary artery occlusion is posited to enable partitioning of vascular resistance into small and large vessels. As such it may have a role in assessment for pulmonary endarterectomy.To test if the occlusion technique distinguished small from large vessel disease we studied 59 subjects with CTEPH, idiopathic PAH, and connective tissue disease (CTD) PAH. At right heart catheterisation, occlusion pressures were recorded. With fitting of the pressure decay curve, PVR was partitioned into downstream (small vessels) and upstream (large vessels, Rup).47 patients completed the study; 14 operable CTEPH, 15 non-operable CTEPH, 13 idiopathic or CTD-PAH, 5 post-operative CTEPH. There was a significant difference in mean Rup in the proximal operable CTEPH group 87.3(95%CI 84.1;90.5); non-operable CTEPH mean 75.8(95%CI 66.76;84.73) p=0.048; and IPAH/CTD, mean 77.1(95%CI 71.86;82.33) p=0.003. ROC curves to distinguish operable from non-operable CTEPH demonstrated an AUC of 0.75, p=0.0001. A cut off of 79.3 gave sensitivity 100%(CI 73.5-100%) but specificity 57.1%(CI 28.9-82.3%). In a subgroup analysis of multiple lobar sampling there was demonstrable heterogeneity.Rup is significantly increased in operable proximal CTEPH compared with non-operable distal CTEPH and IPAH/CTD. Rup variability in patients with CTEPH and PAH is suggestive of pathophysiological heterogeneity.